Ex vivo antimicrobial devices and methods

ABSTRACT

A method and device for destroying and inhibiting exposure to microbes and infection includes a first element and a second element, and a power source. At least one of the elements includes antimicrobial metal, which, when energized by the power source, produces ions that are lethal to microbes. The device can be incorporated into virtually any useful object. During normal use of the object, electrical communication is established between the two elements, causing current supplied from the power source to flow through the antimicrobial metal. The two elements are configured and arranged to ensure that ions flowing from the antimicrobial metal flow through the region in which it is desired to kill microbes. The antimicrobial metal can be on the surface of the element, incorporated into the material making up the element, or provided in any other way that allows the antimicrobial effect to be achieved.

REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 60/882,305, filed Dec. 28, 2006, by the inventors named in thisapplication, the entire content of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates to the prevention of infection and, moreparticularly, to the provision of methods and devices for inhibitingexposure to microbes and infection.

Changes in modern lifestyle have occurred which would have been almostunimaginable even a century ago. An adverse consequence of some of thesechanges has been an increased exposure to harmful microbes. For example,travel between continents is a commonplace experience for manyindividuals. Unfortunately, increased ease of travel facilitatestransfer of potentially disease-causing microbes which were historicallylimited by geography. Another change is the fact that individuals aresurviving bacterial infections, which were previously commonly fatal,due to the advent of antibiotics. People are not the only entities thatare changing and adapting. Adaptation by microbes, fueled by today'smodern antibiotic prescribing practices has resulted in the appearanceof many antibiotic-resistant strains.

The combination of increased exposure to harmful microbes and the morefrequent encounter with antibiotic-resistant organisms contributes to acontinuing need for antibiotic devices and methods. Effective antibioticdevices and methods are required to decrease exposure to microbes duringdaily activities in public places as well as in private homes. Inaddition, reduced exposure to microbes is important in medical anddental settings, such as care facilities, treatment rooms, surgicalsuites and nursing stations.

SUMMARY OF THE INVENTION

Devices and methods are provided for inhibiting exposure to microbes andinfection according to the present invention.

The present invention provides an antimicrobial device, including adevice body having a first electrically conductive element having afirst external surface and a second electrically conductive elementhaving a second external surface, the second element being electricallyisolated from said first element, a first metal component containing anantimicrobial metal disposed on the first external surface of the devicebody, a power source for supplying current to the first metal component,the first and second elements being adapted to being electricallyconnected to each other by an object external to the antimicrobialdevice, whereby current flows through the antimicrobial metal causingmetal ions to flow from the antimicrobial metal toward the object.

The antimicrobial device can be any object used in everyday life,including those specifically identified hereinbelow.

The present invention also provides a method for inhibiting exposure tomicrobes and infection. The method includes the steps of providing adevice having a device body including an antimicrobial metal having afirst external surface and an electrically conductive element having asecond external surface, the second element being electrically isolatedfrom the device body, providing a power source for supplying current tothe device body, and configuring the device body and the electricallyconductive element to cause the device body and the electricallyconductive element to be electrically connected to each other by anobject external to the antimicrobial device when the device is in normaluse, whereby current flows through the antimicrobial metal causing metalions to flow from the antimicrobial metal toward the object.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic circuit diagram of at least a portion of anelectrical circuit included in a device provided by the presentinvention;

FIG. 2 is a view of an embodiment of an antimicrobial doorknob deviceprovided by the present invention;

FIG. 3 is a “killing curve” showing the killing rate of an embodiment ofthe present invention associated with S. aureus;

FIG. 4 is a “killing curve” showing the killing rate of an embodiment ofthe present invention for Escherichia coli;

FIG. 5 is a cross-sectional view of a portion of a further embodimentprovided by the present invention;

FIG. 6 is a cross-sectional view of a portion of a further embodimentprovided by the present invention;

FIG. 7 shows a further embodiment provided by the present invention;

FIG. 8 shows a further embodiment provided by the present invention; and

FIG. 9 shows a further embodiment provided by the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Broadly described, a device for inhibiting exposure to microbes andinfection according to the present invention includes at least twoportions, described herein as a first element and a second element. Eachof these portions has an external surface. At least a firstantimicrobial metal component is disposed on the external surface of thefirst element. Optionally, a second antimicrobial metal component isdisposed on the external surface of the second element.

A power source powers a device according to the present invention. Sucha power source may be any suitable power source, illustrativelyincluding line current or an electrical cell such as an electrochemicalcell or a solar cell. Examples include a battery, a capacitor, andconnection to external AC. One terminal of the power source is inelectrical communication with the first element and the firstantimicrobial metal component. The second terminal of the power sourceis in electrical communication with at least the second element andoptionally with the second antimicrobial metal component, if present.

The first and second elements and the first and second antimicrobialmetal components are electrically insulated from each other by at leastone insulator. The insulator prevents current flow from the firstelement and/or first antimicrobial metal component to the second elementand/or second antimicrobial metal component without completing a circuitthrough at least the first antimicrobial metal component and anelectrical conductor in contact with the surface of the device.

Optionally included in electrical communication with a device accordingto the present invention is circuitry adapted to modulate a current fromthe power source. For example, a resistor, a switch, a signal receiver,a relay, a signal transmitter, transformer, a sensor, or a combinationof these or other such components and connectors may be included,optionally configured as a circuit board arrangement. In a preferredembodiment, all or part of the circuitry adapted to modulate anelectrical current is housed in a cavity in one or more portions of thedevice.

A metal component includes an antimicrobial metal. An antimicrobialmetal is one which inhibits one or more microbes, such as bacteria,protozoa, viruses, and fungi. An antimicrobial metal may bemicrobiocidal or microbiostatic.

Antimicrobial metals include transition metals and metals in columns10-14 of the periodic table. Such metals illustratively include silver,gold, zinc, copper, cadmium, cobalt, nickel, platinum, palladium,manganese, and chromium. In certain embodiments, lead and/or mercury maybe included in amounts not significantly toxic to a user. Highlypreferred is a metal component containing an antimicrobial metal whichgenerates metal ions in response to application of current to the metalcomponent.

A metal component contains an amount of an antimicrobial metal, theamount in the range of 1%-100% by weight of the total composition of themetal component, although in particular embodiments, lower amounts maybe included. In general, a metal component included in an inventivedevice contains an amount of an antimicrobial metal in the range ofabout 1 nanogram to about 1 kilogram. A metal component preferablycontains at least 50 percent by weight of an antimicrobial metal,further preferably contains at least 75 percent by weight of anantimicrobial metal and still further preferably contains at least 95percent by weight of an antimicrobial metal. In another preferredembodiment, the metal component is substantially all antimicrobialmetal. In particular, the metal component is capable of releasing ametal ion when an electrical current is applied to the metal component.

Materials other than an antimicrobial metal may also be included in ametal component. For instance, a metal component may further includemetals which are non-antimicrobial in one configuration according to theinvention, for instance to provide structural support and lower cost ofthe metal component. In an alternative embodiment, a non-metalconstituent is included in the metal component, for instance to providestructural support and lower cost of the metal component. Exemplarynon-metal constituents include such substances as inorganic and organicpolymers, and biodegradable materials. A non-metal constituent ornon-antimicrobial metal included in a metal component may bebiocompatible. Preferably, the metal component is electricallyconductive.

A metal component may be provided in any of various forms,illustratively including, a substantially pure metal, an alloy, acomposite, a mixture, and a metal colloid. Thus, in one embodiment, ametal component is a substance doped with an antimicrobial metal. Forinstance, in a particular example, a stainless steel and/or titaniumalloy including an antimicrobial metal may be included in a metalcomponent.

By example, the antimicrobial properties of silver are particularlywell-characterized and a metal component preferably contains an amountof silver, the amount in the range of 1 percent-100 percent by weight ofthe total composition of the metal component, although lower amounts maybe included in particular embodiments. A metal component preferablycontains at least 50 percent by weight of silver, further preferablycontains at least 75 percent by weight silver and still furtherpreferably contains at least 95 percent by weight silver. In anotherpreferred embodiment, the metal component is substantially all silver.

Copper is also a preferred metal included in a metal component and ametal component preferably contains an amount of copper in the range of1%-100% by weight of the total composition of the metal component,although lower amounts may be included in particular embodiments. In oneembodiment, at least 50% by weight copper is included, furtherpreferably a metal component contains at least 75% by weight copper andstill further preferably contains at least 95% by weight copper. Inanother preferred embodiment, the metal component is substantially allcopper. In particular, the metal component is capable of releasing ametal ion when an electrical current is applied to the metal component.

A combination of metals is also contemplated as included in a metalcomponent. In some instances, certain metals may be more effective atinhibiting growth and/or killing particular species or types ofbacteria. For example, particular metals are more effective atinhibiting growth and/or killing Gram positive bacteria, while othermetals are more effective against Gram negative bacteria as exemplifiedin the Examples described herein.

In a particular embodiment, both silver and copper are included in ametal component. A combination of silver and copper may provide asynergistic antimicrobial effect. For instance, a lesser amount of eachindividual metal may be needed when a combination is used. Additionally,a shorter time during which the device is activated may be indicatedwhere a synergistic effect is observed, allowing for conservation of apower source. The ratio of copper to silver in a metal component mayrange from 1000:1-1:1000. In one embodiment, a metal componentpreferably contains an amount of a copper/silver combination in therange of 1-100 percent by weight of the total composition of the metalcomponent, although lower amounts may be included in particularembodiments. In one embodiment, at least 50 percent by weight of acopper/silver combination is included, further preferably a metalcomponent contains at least 75 percent by weight of a copper/silvercombination and still further preferably contains at least 95 percent byweight of a copper and silver in combination. In another preferredembodiment, the metal component is substantially all copper and silver.

In a further preferred embodiment, a metal which has antimicrobialproperties but which does not have increased antimicrobial propertieswhen an electrical current is applied to the metal is included in ametal component. For example, cadmium has antimicrobial propertieseffective against a wide range of microbes, as described in theExamples, and which are not increased by application of an electricalcurrent. Such a metal is optionally included in a metal component alongwith one or more metals capable of releasing a metal ion when anelectrical current is applied to the metal component. In particularlypreferred embodiments, cadmium and silver, cadmium and copper, orcadmium, silver and copper are included in a metal component. The ratioof one or more metals capable of releasing a metal ion when anelectrical current is applied to the metal component to one or moremetals whose antimicrobial activity is not increased when an electricalcurrent is applied in a metal component may range from about1000:1-1:1000. In one embodiment, a metal component preferably containsan amount of a copper and/or silver and an amount of cadmium such thatthe ratio of copper and/or silver to cadmium is in the range of about1000:1-1:1000. A combination of silver and/or copper and cadmium in ametal component is in an amount in the range of about 1-100 percent byweight of the total composition of the metal component, although loweramounts may be included in particular embodiments. In one embodiment, atleast 50 percent by weight of a copper and/or silver and cadmiumcombination is included, further preferably a metal component containsat least 75 percent by weight of a copper and/or silver and cadmiumcombination and still further preferably contains at least 95 percent byweight of copper and/or silver and cadmium in combination. In anotherpreferred embodiment, the metal component is substantially all copperand/or silver and cadmium. These and other combinations of antimicrobialmetals in a metal component allow for tailoring a device to a specificsituation depending on such factors as likelihood of presence ofparticular microbe type for example.

In a preferred embodiment, the metal component is in the form of acoating disposed on the external surface of the device. The coating canbe applied by any of various methods illustratively including dunkcoating, thin film deposition, vapor deposition, and electroplating. Themetal component in the form of a coating ranges in thickness between1×10⁻⁹-5×10⁻³ meters, inclusive, preferably 1×10⁻⁷-4×10⁻³ meters,inclusive, and more preferably between 0.5×10⁻⁶-5×10⁻⁴ meters inthickness.

It is appreciated that, in the context of preferred embodiments of adevice or system according to the present invention including at leasttwo elements of a device, each element having a metal component, whereinthe metal components are electrically isolated by an insulator, thateach element optionally includes a metal component in the form of ametal-containing coating. In this context, the metal-containing coatingon the one or more elements of the device is preferably present on atleast 50 percent of the external surface of one or both elements of thedevice. More preferably the metal-containing coating on the one or moreelements of the device is preferably present on at least 75 percent ofthe external surface of one or both elements of the device, and furtherpreferably the metal-containing coating on the one or more elements ofthe device is preferably present on substantially all of the externalsurface of the one or more elements of the device. However, an insulatordisposed in a current path between the metal containing coating on thesurface of the one or more elements electrically insulates one elementfrom another and thus does not include a metal-containing coating inelectrical communication with a metal-containing component on the one ormore elements of the device.

A coating may be disposed on a surface of a device in a patternedfashion. For example, interlocking stripes of a metal component and aninsulator may be arranged on a surface of a device. Such a pattern ispreferably designed to inhibit microbes in a continuous region on ornear an inventive device. Thus, the distance between discontinuousregions of a coating is selected to account for the diffusion distanceof ions generated from an antibacterial coating in response to anapplied electrical current. Typically, ions diffuse a distance in therange of about 1-10 millimeters, but diffusion is dependent upon themedium through which the ion will travel.

A metal coating on an element of a device is preferably disposed on anexternal surface as a single continuous expanse of the coating material.

Optionally, the metal component is in the form of a wire, paint, ribbon,or foil disposed on the external surface of a device. Such a metalcomponent may be attached to the device by welding, by an adhesive, orthe like.

In another embodiment, the device may include an antimicrobial metalsuch that the device or portion thereof is the metal component. A secondmetal component may be further included in contact with such a device.Thus, for example, a device or portion thereof may include an alloy ofstainless steel and an antimicrobial metal, and/or an alloy of titaniumand an antimicrobial metal. A commercial example of such a material isstainless steel ASTM grade 30430 which includes 3% copper.

In a further embodiment, a device made of a material including anantimicrobial metal may be formulated such that the antimicrobial metalis distributed non-uniformly throughout the device. For instance, theantimicrobial metal may be localized such that a greater proportion ofthe antimicrobial metal is found at or near one or more surfaces of thedevice.

FIG. 1 illustrates a schematic circuit diagram of at least a portion ofan electrical circuit included in a device according to the presentinvention. A first metal component disposed in electrical connectionwith a first element of an ex vivo device is shown at 320 and a secondmetal component disposed in electrical connection with a second elementof an ex vivo device is shown at 322. Each of the metal components 320and 322 is in electrical communication with a power source 350. As shownin FIG. 1, the first metal component 320 is in electrical communicationwith a first terminal 312 of the power source 350 and the second metalcomponent 322 is in electrical communication with a second terminal 314of the power source 350. Conduits 352 and 354 illustrate electricalconnectors between the first and second metal components 320 and 322 andthe first and second terminals 312 and 314, respectively, of the powersource. Also illustrated are an optional resistor 330 and an optionalswitch 340, each in electrical communication with the power source. Itis noted that the first and second metal components 320 and 322 are notin electrical contact except via the path 352-350-354. In use, anantimicrobial device according to embodiments of the present inventionhas first and second metal components 320 and 322 connected via anelectrical conductor. In particular embodiments, an electrical conductoris not an integral part of an inventive device, the electrical conductoris a microbe, the hand of a user, environmental humidity or other suchconductor.

In an alternative embodiment, one element, either 320 or 322, has apotential charge relative to the other element. When one of theelements, either 320 or 322 is brought into contact with an object thatis relatively neutral or opposite in charge with respect to thenon-contacted element, the charge is dissipated into the object,providing an antimicrobial effect.

An antimicrobial device may be any of various devices which may bebroadly described as having a surface likely to harbor undesirablemicrobes which may then be transferred to an individual who comes incontact with the surface, directly or indirectly. Such devices includeclothing; bed linens, towels, filter masks intended to be worn by ahuman; medical equipment, such as a stethoscope, an endoscope or probe;handheld devices, such as a remote control for an electronic device, aPDA, a headset, an earpiece, a portable or non-portable telephone and apager; processing equipment for consumables such as foods and drugs,such as a meat grinder, a mixer, a food container, and a utensil;ventilation systems and parts therefore, such as an air handler or anair filter; and dispensers of various types, illustratively including atissue dispenser and a paper towel dispenser. Further embodimentsinclude surfaces such as a food preparation surface in a kitchen, anexamination table used by a physician or veterinarian, a laboratorybench, a bathroom surface such as a sink, toilet, bathtub or showersurface, a bathroom accessory, such as a shower or bathmat, a draincover, and a toilet brush. Additional embodiments include personal careaccessories, illustratively including a toothbrush, and a hairbrush orcomb. Hardware devices are provided according to the present invention,illustratively including a doorknob or door handle, a hand railing, adrinking fountain actuator, bathroom hardware and a vehicle steeringwheel.

FIG. 2 illustrates an embodiment of an antimicrobial doorknob device 200according to the present invention. An embodiment of an inventiveantimicrobial doorknob includes at least two portions, a first element202 and a second element 204, each element having an external surface. Afirst antimicrobial metal component 203 is illustrated disposed on theexternal surface of the first element 202. A second antimicrobial metalcomponent 205 is illustrated disposed on the external surface of thesecond element 204.

An internal power source is included in the illustrated embodiment, inthe form of an electrochemical cell, at 208. The power source 208 isdisposed in an internal cavity 207 formed in the second element 204. Oneterminal of the power source is in electrical communication with thefirst element 202 and the first antimicrobial metal component 203. Thesecond terminal of the power source is in electrical communication withthe second element 204 and the second antimicrobial metal component 205.

An insulator 206 is shown which prevents current flow from the firstelement 202 and/or first antimicrobial metal component 203 to the secondelement 204 and/or second antimicrobial metal component 205 withoutcompleting a circuit through the first antimicrobial metal component203, the second antimicrobial metal component and an electricalconductor in contact with the surface of the device (not shown). It isnoted that resistive value of the insulator 206 is greater than theresistive value of the hand or other such electrical conductor thatcompletes the circuit 203 to 205 when touching the doorknob.

An electrical conductor in contact with the surface of the device whichcompletes the electrical circuit may be any suitable electricalconductor. The completion of the circuit allows for current-inducedrelease of antimicrobial metal ions from the one or more antimicrobialmetal components.

In one embodiment, an electrical conductor comes into contact with aninventive device during normal use. For example, in the context of anantimicrobial doorknob, a human hand may serve as an electricalconductor which completes the circuit. Released antimicrobial ionsinhibit growth of microbes transferred from a human hand to a doorknobin regular use and also inhibit transfer of microbes from the doorknobto a hand.

In a further example, a food preparation surface comes into contact withan electrical conductor in the form of a food or moisture in the courseof regular use of the food preparation surface. Thus, in an embodimentof the present invention in the form of a food preparation surface isconfigured such that a food completes the circuit during use of thesurface.

In another embodiment, an electrical conductor may be applied tocomplete the circuit at a desired time. For example, an electricalconductor may be applied at the end of a work period and prior to thebeginning of the next work period. In an illustrative example, such anelectrical conductor is optionally a conductive blanket used to cover awork surface such as a work table or counter at the end of a work day orduring periods of non-use.

A device according to an embodiment of the present invention includesfirst and second elements protruding from a base, such as a toothbrush,bathmat, hairbrush, and comb. FIG. 5 illustrates a cross-section of aportion of one such embodiment 400 showing protrusions 402 extendingfrom a base 403. A first antimicrobial metal component 406 isillustrated disposed on the external surface of the first element 404. Asecond antimicrobial metal component 407 is illustrated disposed on theexternal surface of the second element 405.

A power source (not shown) is connected to the device 400 such that oneterminal of the power source is in electrical communication with thefirst element 404 and the first antimicrobial metal component 406. Thesecond terminal of the power source is in electrical communication withthe second element 405 and the second antimicrobial metal component 407.For example, the terminals may be connected by wires such as shown at409 and 410.

An insulator 408 is shown which prevents current flow from the firstelement 404 and/or first antimicrobial metal component 406 to the secondelement 405 and/or second antimicrobial metal component 407 withoutcompleting a circuit through the first antimicrobial metal component,the second antimicrobial metal component and an electrical conductor incontact with the surface of the device (not shown). In the embodimentshown in FIG. 5, an insulator is an air space 408. Additionally, thebase 403 is configured so as to prevent flow of current from 404/406 to405/407 without completing a circuit through the first antimicrobialmetal component, the second antimicrobial metal component and anelectrical conductor in contact with the surface of the device. Anelectrical conductor completing the circuit is illustratively a liquidor gel used in tooth cleaning, such as saliva, toothpaste and/or water,a body part contacting the device, such as a human hand, foot and/orscalp.

FIG. 6 illustrates a cross-section of a portion of a further embodimentof a device 500 according to an embodiment of the present inventionincluding multiple protrusions 502 extending from a base 503. Theprotrusions 502 shown include a first antimicrobial metal component 506is illustrated disposed on the external surface of the first element504. A second antimicrobial metal component 507 is illustrated disposedon the external surface of the second element 505.

A power source (not shown) is connected to the device 500 such that oneterminal of the power source is in electrical communication with thefirst element 504 and the first antimicrobial metal component 506. Thesecond terminal of the power source is in electrical communication withthe second element 505 and the second antimicrobial metal component 507.For example, the terminals may be connected by wires such as shown at509 and 510.

An insulator 508 is shown which prevents current flow from the firstelement 504 and/or first antimicrobial metal component 506 to the secondelement 505 and/or second antimicrobial metal component 507 withoutcompleting a circuit through the first antimicrobial metal component,the second antimicrobial metal component and an electrical conductor incontact with the surface of the device (not shown). In an embodimentshown in FIG. 6, a further insulator is an air space 512. Additionally,the base 503 is configured so as to prevent flow of current from 504/506to 505/507 without completing a circuit through the first antimicrobialmetal component, the second antimicrobial metal component and anelectrical conductor in contact with the surface of the device. Anelectrical conductor completing the circuit is illustratively a liquidor gel used in tooth cleaning, such as saliva, toothpaste and/or water,a body part contacting the device, such as a human hand, foot and/orscalp.

FIG. 7 illustrates an embodiment of an inventive device 600. A device600 provides a surface which can be incorporated in various devices forantimicrobial effect illustratively including fabric-based article suchas an article of clothing, a towel, and/or bed linens such as sheets andblankets; a filter mask; an item of medical equipment; a handheldelectronic device; an item of processing equipment for a consumable; aventilation system component; a wipe dispenser; a food preparationsurface; an examination table for a human or an animal; a laboratorybench; a bathroom surface; a bathroom accessory; a personal careaccessory; and a hardware apparatus. An inventive device 600 includes aplurality of antimicrobial metal components disposed on the externalsurface of a plurality of first elements 602, and a plurality of secondelements 604, labeled “grounding material.” Optionally, a plurality ofsecond antimicrobial metal components is disposed on the externalsurface of at least one of the plurality of second elements.

Each of the individual first and second elements are separated by aninsulator 606. The size of the insulator and thus the size of theseparation between an individual first element and an individual secondelement is selected to optimize an antimicrobial effect. In general, aninsulator is dimensioned such that an individual first element and anindividual second element are separated by about 0.1 micron-10 cm,inclusive, although not limited to this range of sizes.

A power source 608 is connected to the device 600 such that one terminalof the power source is in electrical communication with the plurality offirst elements and the plurality of first antimicrobial metalcomponents. The second terminal of the power source is in electricalcommunication with the plurality of second elements.

In a further embodiment, an antimicrobial device is provided whichincludes a device body having a first element having a first externalsurface and a second element having a second external surface, a firstmetal component containing an antimicrobial metal disposed on the firstexternal surface of the device body, a power source having a firstterminal and a second terminal, the first terminal in electricalcommunication with the first metal component; and an insulator placed ina current path between the first terminal of the power source and thesecond terminal of the power source preventing current flowing from thefirst terminal from reaching the second terminal, wherein activation ofthe power source creates a potential between the first element and thesecond element such that placement of an object in contact with theantimicrobial metal results in movement of metal ions from theantimicrobial metal toward the object.

An exemplary embodiment of such an inventive device 700 is shown in FIG.8. An antimicrobial device 700 includes an antimicrobial metal componentdisposed on the external surface 702 of a first element 704. Asdescribed above, a first element and/or second element is optionallyfabricated partially or wholly from an antimicrobial metal. A secondelement, 706, labeled “grounding material,” is depicted and the firstand second elements, 704 and 706, respectively, are separated by aninsulator 708, labeled “insulating material” in FIG. 8. The size of theinsulator and thus the size of the separation between the first elementand the second element is selected to optimize an antimicrobial effect.In general, an insulator is dimensioned such that an individual firstelement and an individual second element are separated by about 0.1micron-10 cm, inclusive, although not limited to this range of sizes.

A power source 710 is connected to the device 700 such that one terminalof the power source is in electrical communication with the firstelement and the first antimicrobial metal component. The second terminalof the power source is in electrical communication with the secondelement.

A device according to the present invention is optionally directlygrounded or may use a “floating” ground.

In an embodiment such as shown in FIG. 8, a potential is created betweenthe antimicrobial metal 702 and the second element 706. When an object,not shown, which is neutral or negatively charged with respect to thesurface 702 is placed in contact with the surface 702, metal ions fromthe antimicrobial metal move towards the object, providing anantimicrobial effect. It is noted that a circuit is not completed by theobject in an embodiment as illustrated in FIG. 8. The object isillustratively an object typically used in conjunction with the deviceor which otherwise comes in contact with the device. For example, wherethe device 700 is incorporated in a food preparation surface, the objectis illustratively a food item, a utensil, a user's hand and/or amicrobe. A device 700 is optionally incorporated in antimicrobialdevices of various types, illustratively including a fabric-basedarticle such as an article of clothing, bed linens, and/or a towel; afilter mask; an item of medical equipment; a handheld electronic device;an item of processing equipment for a consumable; a ventilation systemcomponent; a wipe dispenser; a food preparation surface; an examinationtable for a human or an animal; a laboratory bench; a bathroom surface;a bathroom accessory; a personal care accessory; and/or a hardwareapparatus.

FIG. 9 illustrates an embodiment including a first component includingan antimicrobial metal in the form of a “coating material,” a secondcomponent labeled “base material” and an insulator labeled “insulatinglayer” disposed between the coating material and base material. FIG. 9graphically illustrates silver ions moving towards bacteria in contactwith the first component, the silver ions providing an antimicrobialeffect on the bacteria.

Embodiments of inventive compositions and methods are illustrated in thefollowing examples. These examples are provided for illustrativepurposes and are not considered limitations on the scope of inventivecompositions and methods.

EXAMPLE 1

Procedures to identify an antimicrobial metal composition for use in anincluded metal component may include an examination of each metal'santimicrobial potential using a panel of common Gram (+) and Gram (−)bacterial, fungal species or other microbes. a method adapted from theKirby Bauer agar gel diffusion technique, the antimicrobial efficacy ofeight metals: silver, copper, titanium, gold, cadmium, nickel, zinc andstainless steel AISI 316L and their electrically generated ionic formsare tested against 5 bacterial species and one fungus.

Strains of Escherichia coli, S. aureus, Pseudomonas aeruginosa,Enterococcus faecalis, Methicillin resistant S. aureus (MRSA), andCandida albicans isolated from samples submitted to the PennsylvaniaState University Animal Diagnostic Laboratory (E. coli, S. aureus, P.aeruginosa and E. faecalis) or J.C. Blair Hospital, Huntingdon, Pa.(MRSA and C. albicans), are diluted to a 0.5 MacFarland standard andinoculated onto Mueller-Hinton agar plates (Remel, Lenexa, Kans.).

Metallic wires served as the ion source, specifically: silver (99.97%purity), copper (99.95+% purity), titanium (99.8% purity), gold (99.99%purity), cadmium (99.999% purity), nickel (99.98% purity), zinc (99.999%purity) and stainless steel AISI 316L. All wires are of uniform equaldiameter (1.0 mm).

Small holes are burned into opposite sides of the Petri plates whichallowed for the aseptic threading of 32 mm lengths of test wire into theagar. Once embedded, 1 cm2 of wire surface area is exposed to thegrowing microbes.

Electrical currents are generated by placing a standard 1.55 Volt AAbattery in series with one of the following resistors: 3.01 MΩ, 1.5 MΩ,150 kΩ, and 75 kΩ. A 70 mm length of each of the test metals isconnected in series with the given resistor. The current that isgenerated by each of the four different resistors (3.01 MΩ, 1.5 MΩ, 150kΩ, and 75 kΩ) is 0.5 μA, 1.0 μA, 10 μA, and 20 μA respectively. The 20μA/cm2 surface area charge is proven in 1974 to be a safe electricalexposure value for the cells. (Barrnco 1974) As calculated withFaraday's equation, a 20 μA/cm² surface area charge density producedover 80 μg/hour of silver ions.

The circuit is completed by aseptically threading the anode through theopposite hole and embedding it into the agar. One control plate for eachmicrobial species is aseptically threaded with wires, but received noelectrical current. The plates are incubated in ambient air at 37° C.for 24 hours, and subsequently examined for bacterial growth and/orzones of inhibition.

Of the eight metals and metal ions tested, silver ions and cadmium showbactericidal efficacy against all bacterial species tested, and copperions showed bactericidal efficacy against Gram-positive bacteria.Titanium, gold, nickel, zinc and stainless steel AISI had no significanteffects in this example.

Exemplary results are shown in Table 1 in which numbers representmeasurements of the diameter of the zone of inhibition in millimetersaround the central wire. The table shows that silver has somemicrobiocidal properties when not electrically ionized, since E. coli isinhibited by non-charged silver. A smaller current produced resultssimilar to larger currents, and in all cases the addition of currentincreased the size of the inhibition zone.

Copper also shows antimicrobial properties, both in the ionic form andthe uncharged metallic form, as summarized in Table 1. In the unchargedform copper showed bactericidal properties against E. faecalis. Aminimal current produced bactericidal results for all Gram (+) speciesof bacteria, and higher currents produced larger zones. Copper did nothave an effect on Gram (−) bacterial species at currents used.

Surprisingly, cadmium results are unique in producing antimicrobialeffects against all organisms tested, and the pattern of efficiency heldtrue both in the absence and presence of electrical stimulation.Increasing the current resulted in minimal changes in microbialresponse. Cadmium produced a double zone of inhibition: an inner zone ofcomplete clearing closer to the wire, and an outer zone of decreasedbacterial growth (incomplete clearing). For descriptive purposes, theinner zone is considered to be “microbiocidal”, while the outer zone isconsidered “microbistatic”, or inhibitory. Numbers shown in Table 1reflect this double zone of inhibition such that the size of the “innerzone” is present first and the size of the “outer zone” is presented inparentheses. Additionally, cadmium consistently showed some inhibitoryeffect in the absence of electrical charge; increasing the current hadlittle additional effect.

TABLE 1 Gram Positive Gram Negative Fungus Current S. aureus E. faecalisMRSA E. coli P. aeruginosa C. albicans Silver 0 μA 6 0 0 5 0 0 0.5 μA 1817 18 20 18 34 1 μA 20 19 18 21 21 30 10 μA 20 21 18 25 21 32 20 μA 2020 18 24 20 30 Gold 0 μA 3 0 0 0 0 0 0.5 μA 0 0 0 0 0 0 1 μA 0 0 0 10 00 10 μA 0 0 0 0 0 0 20 μA 0 0 0 0 0 0 Titanium 0 μA 0 0 0 0 0 0 0.5 μA 00 0 0 0 0 1 μA 0 0 0 0 0 0 10 μA 0 0 0 0 0 0 20 μA 0 0 0 0 0 0 Copper 0μA 0 11 0 0 0 0 0.5 μA 14 16 7 0 0 0 1 μA 6 16 6 0 0 0 10 μA 0 15 9 0 00 20 μA 8 18 11 0 0 0 Stainless steel 0 μA 0 0 0 0 0 0 0.5 μA 0 0 0 0 00 1 μA 0 0 0 0 0 0 10 μA 0 0 0 0 0 0 20 μA 0 0 0 0 0 0 Cadmium 0 μA8(15) 5 14 6(18) (17) 28 0.5 μA 6(10) 6 13 5(18) (12) 28 1 μA 8(15) 6 134(18) (18) 31 10 μA 6(14) 5 15 6(18) (16) 30 20 μA 7(15) 5 16 5(17) (18)30 Zinc 0 μA 0 0 0 0 0 0 0.5 μA 0 0 0 0 0 0 1 μA 0 0 0 0 0 0 10 μA 0 0 00 0 0 20 μA 0 0 0 0 0 0 Nickel 0 μA 0 0 0 0 0 0 0.5 μA 0 0 0 0 0 0 1 μA0 0 0 0 0 0 10 μA 0 0 0 0 0 0 20 μA 0 0 0 0 0 0

EXAMPLE 2 Characterization of Effective Antimicrobial Metals

A “killing curve analysis” may be performed in order to characterizeparameters which achieve an antimicrobial effect. A predetermined numberof colony forming units/ml (CFU/ml), established in a growth medium, aretransferred to a saline solution and then exposed to the antimicrobialmetal or metal form. At predetermined time intervals, an aliquot isremoved, diluted (if necessary), inoculated onto blood agar plates andincubated overnight at 37° C. The resulting growth is quantified asCFU/ml. A graph, with time as the X-axis and CFU/ml as the Y-axisdemonstrates the point at which the antimicrobial effect and microbialpopulation growth intersect. The concentration of metal required forantimicrobial effect can be determined by examining the time point atwhich the microbial population begins to decrease.

To examine the rate of diffusion of ions away from the metal source,i.e. the rate at which the microbes are inhibited from growing (orkilled), high performance microscopy may be used. A high performancemicroscopic system developed by Cytoviva allows for real-timeobservation of living cells and cellular components without the use ofstaining agents. By observing the microbial response to a given metal, a“velocity” of microbial destruction can be directly observed. The rateof diffusion of ions through agar can be inferred from the velocity ofkill.

In this example, silver is tested with respect to two differentbacterial species, E. coli and S. aureus. A current of 0.5 μA is used inthis example.

Strains of E. coli and S. aureus isolated from samples submitted to thePennsylvania State University Animal Diagnostic Laboratory, areseparately diluted to a 0.5 MacFarland standard and added to individualtest tubes containing 10 mls of sterile Tryptic Soy Broth (TSB). Asilver wire (99.97% purity) having a uniform diameter of 1.0 mm servedas a source of ions.

Two small holes are burned into the screw cap of each test tube. SilverWires (99.97% purity), having uniform diameters of 1.0 mm, served as ionsources. The wires are aseptically threaded through the screw cap holesand positioned to expose a total length of 32 mm into the previouslyinoculated TSB. This resulted in the exposure of 1 cm² of silver wire togrowing bacterial cells. Electrical current is generated by placing astandard 1.55 Volt AA battery in series with a 3.01 MΩ resistor. Thecurrent that is generated by the 3.01 MΩ resistor is 0.5 μA whencombined into the circuit. Additionally a circuit, formed without anyresistor is utilized and inserted into a tube in an identical fashion.The circuits are completed by aseptically threading the anode throughanother hole in the test tube screw cap and into the TSB. One tube ofeach bacterial species, serves as the control. It contained a silverwire, but no external circuit is connected. The silver wire as well asthe anode wire is placed in contact with the bacterially laden brothcontinued within the test tube. This setup is used to produce “killingcurves”.

The tubes are incubated in air at room temperature for a total of 8hours. Every hour the test tube is vortexed for approximately 10seconds. The test tube cap is then opened and a 10 μl sample of broth isaseptically drawn from the test tube. The test tube are again closed andvortexed. The sample is plated onto blood agar plates using a spiralplating technique. The blood agar plates are incubated at roomtemperature for 24 hours. The number of colonies present on the bloodagar plates at 24 hours are counted and recorded.

The results clearly demonstrate that the charged form of the silvermetal has a much greater kill rate when compared to the non-chargedmaterial. A “killing curve” shown in FIG. 3 shows the killing rateassociated with S. aureus. The results clearly demonstrate a bacterialreduction rate of approximately 5.698*10E12 bacteria per hour. Withinthis time frame both the control and the silver with no resistor allowbacterial growth.

A “killing curve” for Escherichia coli in FIG. 4 shows the killing rateassociated with E. coli. The 3 MΩ resistor utilized in this circuitcorresponds to the smallest current 0.5 uA. The curve shows bacterialreduction from 320*10E6 to zero within five hours, a rate ofapproximately 72*10E6 bacteria per hour. Within this time period boththe control and the silver with no resistor tests continue to supportbacterial growth.

EXAMPLE 3 Optimization of Critical Operational Parameters ofAntimicrobial Metals

Antimicrobial properties of specific metals or metal forms differ whenmodifications are made in the experimental parameters. Using data fromthe “killing curve analyses”, critical parameters will be establishedfor the generation of optimal antimicrobial effects, and can then bebalanced against the characteristics of the application into which themetal will be incorporated.

In order to evaluate any possible toxicity of antimicrobial metalcompositions on mammalian cells, in vitro cell culture systems may beutilized. Specifically, batteries and resistors connected in series witha predetermined antimicrobial metal composition is aseptically threadedinto a mammalian cell culture flask and allowed to run, generating metalions within the culture. Cells are monitored during testing formorphological changes and percentages of live vs. dead cells. Inaddition, treated and control cells may be evaluated via metabolicfunction assays such as albumin and urea levels in hepatocytes; bonealkaline phosphatase levels in osteoblasts; and matrix protein levels inchrondrocytes.

In addition, the effects of circuit polarity, operation time and dutycycle are evaluated on cells in vitro using device parameters andoptimized for maximal antimicrobial effect and low toxicity. An externalcircuit is constructed allowing for varying run-time cycles andalternating circuit polarities. The external circuit with battery,resistor, an inverter for reversing polarity, and a timer will beconnected in series with the test antimicrobial metal. The circuit willbe aseptically threaded into the cell culture flask and allowed to run,generating antimicrobial ions within the culture. The continuous runningtime of the circuit as well as the polarity of the circuit will bemanipulated by varying the circuit timer and changing the polarity ofthe circuit via the switch.

Any patents or publications mentioned in this specification areincorporated herein by reference to the same extent as if eachindividual publication is specifically and individually indicated to beincorporated by reference.

The compositions and methods described herein are presentlyrepresentative of preferred embodiments, exemplary, and not intended aslimitations on the scope of the invention. Changes therein and otheruses will occur to those skilled in the art. Such changes and other usescan be made without departing from the scope of the invention as setforth in the claims.

1. An antimicrobial device, comprising: a device body having a firstelement having a first external surface and a second element having asecond external surface; a first metal component containing anantimicrobial metal disposed on the first external surface of the devicebody; a power source having a first terminal and a second terminal, thefirst terminal in electrical communication with the first metalcomponent; and an insulator placed in a current path between the firstterminal of the power source and the second terminal of the power sourcepreventing current flowing from the first terminal from reaching thesecond terminal without completing a circuit including an electricalconductor adjacent to the external surface of the device.
 2. Theantimicrobial device of claim 1 wherein the device body is included inan apparatus selected from the group consisting of: a fabric-basedarticle such as an article of clothing, bed linens, and/or a towel; afilter mask; an item of medical equipment; a handheld electronic device;an item of processing equipment for a consumable; a ventilation systemcomponent; a wipe dispenser; a food preparation surface; an examinationtable for a human or an animal; a laboratory bench; a bathroom surface;a bathroom accessory; a personal care accessory; and a hardwareapparatus.
 3. The antimicrobial device of claim 1 wherein the devicebody is included in a handheld electronic device selected from the groupconsisting of: a remote control, a PDA, a headset, an earpiece, atelephone and a pager.
 4. The antimicrobial device of claim 1 whereinthe device body is included in a food processing apparatus selected fromthe group consisting of: a meat grinder, a mixer, a food container, anda utensil.
 5. The antimicrobial device of claim 1 wherein the devicebody is included in a bathroom apparatus selected from the groupconsisting of: a sink, toilet, bathtub and shower.
 6. The antimicrobialdevice of claim 1 wherein the device body is included in a bathroomaccessory selected from the group consisting of: a bathmat, a showermat,a drain cover, and a toilet brush.
 7. The antimicrobial device of claim1 wherein the device body is included in a personal care accessoryselected from the group consisting of: a toothbrush, a hairbrush and acomb.
 8. The antimicrobial device of claim 1 wherein the device body isincluded in a hardware apparatus selected from the group consisting of:a doorknob, a door handle, a hand railing, a drinking fountain actuator,and a vehicle steering wheel.
 9. The antimicrobial device of claim 1,further comprising a second metal component containing an antimicrobialmetal, the second metal component disposed on the second externalsurface, wherein the second terminal is in electrical communication withthe second metal component and wherein the insulator insulates the firstmetal component from the second metal component.
 10. The antimicrobialdevice of claim 9, wherein the first metal component, the second metalcomponent, or both the first metal component and the second metalcomponent, is a metal-containing coating
 11. The antimicrobial device ofclaim 1, wherein the metal component comprises a metal selected from thegroup consisting of: silver; copper; both silver and copper; both silverand cadmium; both copper and cadmium; and a combination of silver,copper and cadmium.
 12. The antimicrobial device of claim 1, wherein themetal component comprises a metal selected from the group consisting of:gold, zinc, cobalt, nickel, platinum, palladium, manganese, chromium;and a combination thereof.
 13. The antimicrobial device of claim 10,wherein the metal coating ranges in thickness between 1×10⁻⁹-5×10⁻³meters
 14. The antimicrobial device of claim 10, wherein the metalcoating is disposed on a portion of a combined surface area of the firstexternal surface and the second external surface, the portion of thecombined surface area ranging from 1-100% of the combined surface area,excluding any portion of an external surface of the device occupied bythe insulator
 15. The antimicrobial device of claim 10, wherein themetal coating comprises at least a first region of coating on the firstexternal surface and at least a second region of coating on the secondexternal surface, the first region of coating in electricalcommunication with the first terminal and the second region of coatingin electrical communication with the second terminal, wherein theinsulator is placed in the current path between the first terminal ofthe power source and the second terminal of the power source and whereinthe insulator electrically insulates the first region of coating on thefirst external surface from the second region of coating on the secondexternal surface.
 16. The antimicrobial device of claim 1, wherein themetal component is in the form of a wire disposed on the externalsurface.
 17. An antimicrobial device, comprising: a device body having afirst element having a first external surface and a second elementhaving a second external surface; a first metal component containing anantimicrobial metal disposed on the first external surface of the devicebody; a power source having a first terminal and a second terminal, thefirst terminal in electrical communication with the first metalcomponent; and an insulator placed in a current path between the firstterminal of the power source and the second terminal of the power sourcepreventing current flowing from the first terminal from reaching thesecond terminal, wherein activation of the power source creates apotential between the first element and the second element such thatplacement of an object in contact with the antimicrobial metal resultsin movement of metal ions from the antimicrobial metal toward theobject.
 18. An antimicrobial device, comprising: a device body having afirst electrically conductive element having a first external surfaceand a second electrically conductive element having a second externalsurface, said second element being electrically isolated from said firstelement, a first metal component containing an antimicrobial metaldisposed on the first external surface of the device body; a powersource for supplying current to the first metal component; and saidfirst and second elements being adapted to being electrically connectedto each other by an object external to said antimicrobial device,whereby current flows through said antimicrobial metal causing metalions to flow from said antimicrobial metal toward the object.
 19. Theantimicrobial device recited by claim 18 wherein said first and secondelements are adapted to be electrically connected to each other by thehand of a user of said antimicrobial device.
 20. The antimicrobialdevice recited by claim 18 wherein said first and second elements areadapted to be electrically connected to each other by one or moremicrobes.
 21. The antimicrobial device recited by claim 18 wherein saidfirst and second elements are adapted to be electrically connected toeach other by environmental humidity.
 22. The antimicrobial devicerecited by claim 18 wherein said first and second elements are embodiedin a work surface, and are adapted to be electrically connected to eachother by food placed on said work surface.
 23. The antimicrobial devicerecited by claim 18 wherein said first and second elements are embodiedin a work surface, and are adapted to be electrically connected to eachother by a conductive blanket placed on said work surface.
 24. Theantimicrobial device recited by claim 18 wherein said first and secondelements are adapted to be embodied in a holder for an object bearingmicrobes that are to be destroyed, said first and second elements beingadapted to be electrically connected to each other by the object. 25.The antimicrobial device recited by claim 24 wherein the object is acomb.
 26. The antimicrobial device recited by claim 24 wherein theobject is a toothbrush.
 27. The antimicrobial device recited by claim 18wherein said first and second elements are adapted to be electricallyconnected to each other by textiles.
 28. The antimicrobial devicerecited by claim 27 wherein the textiles are clothing.
 29. Theantimicrobial device of claim 1 wherein the device body is a hand dryer.30. The antimicrobial device of claim 1 wherein the device body is adoor push plate.
 31. The antimicrobial device of claim 1 wherein thedevice body is selected from the group consisting of: a keypad, computerkeyboard and a computer mouse.
 32. The antimicrobial device of claim 1wherein the device body is a counter top.
 33. The antimicrobial deviceof claim 1 wherein the device body is a shopping cart handle.
 34. Theantimicrobial device of claim 1 wherein the device body is a child'stoy.
 35. The antimicrobial device of claim 1 wherein the device body isa child's accessory.
 36. The antimicrobial device of claim 1 wherein thedevice is sterilization apparatus.
 37. The antimicrobial device of claim27 wherein the device is a textile selected from the group consisting ofmedical or veterinary bandages and dressings.
 38. An antimicrobialdevice, comprising: a device body including an antimicrobial metalhaving a first external surface and an electrically conductive elementhaving a second external surface, said second element being electricallyisolated from said device body, a power source for supplying current tosaid device body; and said device body and said electrically conductiveelement being adapted to being electrically connected to each other byan object external to said antimicrobial device, whereby current flowsthrough said antimicrobial metal causing metal ions to flow from saidantimicrobial metal toward the object.
 39. The antimicrobial devicerecited by claim 38 wherein said antimicrobial metal includes an alloy.40. The antimicrobial device recited by claim 39 wherein said alloy is3% copper.
 41. A method for inhibiting exposure to microbes andinfection comprising the steps of: providing a device having a devicebody including an antimicrobial metal having a first external surfaceand an electrically conductive element having a second external surface,said second element being electrically isolated from said device body,providing a power source for supplying current to said device body; andconfiguring said device body and said electrically conductive element tocause said device body and said electrically conductive element to beelectrically connected to each other by an object external to saidantimicrobial device when said device is in normal use, whereby currentflows through said antimicrobial metal causing metal ions to flow fromsaid antimicrobial metal toward the object.